Snakes Resist Toad Toxins

Mar 15, 2016

Utah State University researchers have pinned down the genetic mutations that allow certain species of snakes to resist toad toxins.


A gartersnake (Thamnophis sirtalis) eating a toad (Anaxyrus woodhousei)
Credit Colorado State University

If you eat a toad, toxins in its skin will attach to your muscle cells, disabling the mechanism that allows them to relax, which strengthens and prolongs their contractions. This is especially dangerous if the toxins reach one of your most important muscles—your heart.

“What we were trying to do was see how bufadienolides, which are toad toxins, affect the whole body physiology of snakes.”

PhD student Shab Mohammadi and her colleagues in the USU Department of Biology recently published a new study the journal Toxicon describing their findings. They used data from two species of snakes: watersnakes from Louisiana, which normally eat fish and amphibians, and gophersnakes, more familiarly known in Utah as blowsnakes, which eat small mammals. DNA sequences of these two species showed that watersnakes had mutations to the gene that makes the toxin’s target, whereas gophersnakes have the same DNA sequences as humans, mice, and other non-resistant organisms.

“When we inject really small quantities of this toxin in gophersnakes, they don’t survive. And, the reaction of the gophersnakes is similar to what a mammal, or a human, would experience if they were also exposed to these levels of toad toxins.”

Even at the highest dosage, watersnakes were unaffected, whereas the lowest dose was lethal to the gophersnakes. Mohammadi and her coauthors concluded that the mutations they observed were responsible for the differences in lethality between the two snake species. Although most people will never be poisoned by a toad, they may benefit from drugs modeled on the toad’s poisons, which can help treat preeclampsia, hypertension, and heartbeat abnormalities.